C9orf72 and amyotrophic lateral sclerosis: To assess if the relationship between C9orf72 repeat expansion and telomere repeat size was specific to C9orf72-mediated ALS, we ran ExpansionHunter on three ALS genes which also contain disease-associated repeat expansions: ATXN1, ATXN2, and NIPA1. There was no difference in telomere length observed between expansion carriers and non-expansion carriers for any of these genes.